nichrome wire around a fuse
Electric igniters are made by wrapping a segment of nichrome wire around a standard fuse segment. To make a fuse, you’ll need:
- a segment of fuse
- nichrome wire
- solid core wire
- hot glue gun
- electrical tape
- large gauge wire for cabling
When a current of about an amp is run through small gauge nichrome wire, it will glow orange. This is hot enough to spark ignition in a gun powder filled fuse.
We will be running the entire ignition system off of a 12V sealed lead-acid battery, the type used in UPS backup power supplies. This can provide the high current needed to sustain an amp through the nichrome for several seconds and last for the duration of a fireworks show.
Powered Nichrome
We want approximately an amp through the nichrome, so at 12V we want about 10 ohms of resistance in the of nichrome wire (accounting for a couple ohms of resistance in the 10 feet of connection cables). This equates to about an inch of nichrome wire to wrap around the fuse. Too short and the higher current will cause it to get too hot and break before igniting the fuse. Too long and it wont reach a glowing hot temperature and fail to ignite the fuse. This may take some experimentation to see what length of nichrome will provide a steady glow for your wire gauge (be sure to test with the connection cables as they add some resistance). After wrapping the nichrome, hold it in place with hot glue and tape the ends onto the solid wire.
Fuse cable bundle
The ends of the nichrome are wrapped around solid core wire that are then connected to a long cable to the ignition box. For this we chose speaker wire, it comes paired and in fairly large gauge (18 AWG) for low resistance when carrying the 1 amp of current to power the nichrome. Each speaker wire is color coded for matching the connector end with the fuse end so you can trace which launch code corresponds to which fuse. 4-pin quick connect housings were used to connect to the ignition board, so two igniter cables per connection. Each half of the ignition box can support 10 igniters, so speaker cables were grouped into bundles of 10 and also color coded. Then every igniter can be identified by a bundle color & cable color. Eg. the bottom igniter in this photo would be Grey/Black.
